1. Field of the Invention
This invention pertains to rotating clutches which are activated by means of a hydraulically actuated pressure plate to cause frictional contact between plates to transfer energy and is applicable to both multiplate clutches and single plate clutches used in power transmission systems.
2. Background Art
There are many types of actuation systems for rotating disk clutches many of which include the use of a pressure plate. In the case of some multiplate disk clutches the pressure plate is moved against a first plate of a series of plates to cause frictional contact between adjoining plates where alternate plates are keyed to two different i.e., driving and driven members. Movement or actuation of a pressure plate can be mechanical, hydraulic or electrical. The present invention pertains to the type of clutch in which a pressure plate is activated hydraulically, as for example U.S. Pat. No. 4,036,344 to Nolan, or Hilpert U.S. Pat. No. 3,360,087 and White U.S. Pat. No. 3,814,226 cited in Nolan. Although the Nolan patent is directed to a two stage or multiple element clutch as a means for reducing drag when the clutch is not operating, the portion which is pertinent to the present invention is the application of hydraulic fluid under pressure to chamber 55 to force piston or pressure plate 48 to move axially to press plates 26 and 34 together and against stop 36 so as to cause the driven member 10 to which alternate plates 26 are keyed to be driven by driving member 28 to which alternate plates 34 are keyed. Nolan's hydraulic activation system to deliver hydraulic pressure through passageway 56 and conversely to relieve that pressure for inactivation of the clutch is not shown but the return spring 64 used by Nolan for clutch disengagement is shown. U.S. Pat. No. 4,333,552 to LaMarche is directed to a more intricate, sophisticated arrangement for operation of a pressure relief valve in hydraulically actuated clutches.
Other more simple systems, as for example the references cited in Nolan, contemplate the direct connection of driven and driving members by hydraulically forcing a rotating or rotatable element against a single plate or a stack of plates for frictional contact. In other systems, and particularly those not using spring biasing for disengagement, clutch actuation and release can be degraded by actions and reactions within the hydraulic system. For example, the viscous action of hydraulic fluid remaining in the system on clutch release can maintain a force on the driven member which would interfere with gear engagement in an attached transmission. Hydraulic actuators are sometimes provided with relief systems to drain or partially drain the hydraulic pressure chamber. Relief systems can, in turn, create a delay in actuation when a substantial volume of hydraulic fluid is necessary to fill the actuation chamber prior to causing a movement of the pressure plate in response to hydraulic pressure.